title: Inactivation kinetics of three Listeria monocytogenes strains under high hydrostatic pressure.
abstract: High hydrostatic pressure (HHP) inactivation of three Listeria monocytogenes strains (EGDe, LO28, and Scott A) subjected to 350 MPa at 20 degrees C in ACES buffer resulted in survival curves with significant tailing for all three strains. A biphasic linear model could be fitted to the inactivation data, indicating the presence of an HHP-sensitive and an HHP-resistant fraction, which both showed inactivation according to first-order kinetics. Inactivation parameters of these subpopulations of the three strains were quantified in detail. EGDe showed the highest D-values for the sensitive and resistant fraction, whereas LO28 and Scott A showed lower HHP resistance for both fractions. Survivors isolated from the tail of LO28 and EGDe were analyzed, and it was revealed that the higher resistance of LO28 was a stable feature for 24% (24 of 102) of the resistant fraction. These HHP-resistant variants were 10 to 600,000 times more resistant than wild type when exposed to 350 MPa at 20 degrees C for 20 min. Contrary to these results, no stable HHP-resistant isolates were found for EGDe (0 of 102). The possible effect of HHP survival capacity of stress-resistant genotypic and phenotypic variants of L. monocytogenes on the safety of HHP-processed foods is discussed.
authors.affiliation: Top Institute for Food and Nutrition, P.O. Box 557, 6700 AN Wageningen, The Netherlands. ineke.vanboeijen@wur.nl
authors.forename: Ineke K H
authors.initials: IK
authors.lastname: Van Boeijen
authors.forename: Roy
authors.initials: R
authors.lastname: Moezelaar
authors.forename: Tjakko
authors.initials: T
authors.lastname: Abee
authors.forename: Marcel H
authors.initials: MH
authors.lastname: Zwietering
mesh_terms: D015169:Colony Count, Microbial / Q000379:methods*; D005516:Food Microbiology; D006874:Hydrostatic Pressure; D007700:Kinetics; D008089:Listeria monocytogenes / Q000254:growth & development*; D008954:Models, Biological; D013696:Temperature; D013997:Time Factors